This invention relates to synthetic lubricant base stocks based on silane chemistry and to chemical intermediates useful in their preparation. More particularly, it relates to a novel family of trisilahydrocarbons prepared from di halo silane, diolefins, trihalo- and trialkylsilanes, and organometallic and hydridometallic compounds through novel alkenylhalosilane intermediates.
Deficiencies in the properties and stability of petroleum base stocks historically used in the formulation of lubricants, hydraulic fluids, and functional fluids have led to the development of a wide variety of synthetic base stocks--for example, polyalphaolefins, esters, silicones, perfluorinated polyethers, and the like. These base stocks which are prepared through specific chemical syntheses rather than by the refining of crude oils, have numerous advantages over conventional petroleum oils. They are particularly useful in aerospace, military, and other specialty applications which involve extremes of temperature, vacuum, hostile chemical environments, and the like, in which conventional petroleum-based products do not hold up.
Among the classes of synthetic lubricant base stock that have shown promise in many of these specialty applications are the alkylsilanes or monosilahydrocarbons, EQU CH.sub.3 --Si (R'R"R'")
wherein R', R", and R'" are alkyl groups having from six to twelve carbon atoms. These monosilahydrocarbons are described, for example, in C. E. Snyder et al., ASLE Transactions, vol. 25, No. 3, pp. 298-308 (1982). These monosilahydrocarbons have been shown to be superior to synthetic hydrocarbons such as the polyalphaolefins in viscosity-temperature properties, oxidative stability, and especially thermal stability, while additionally having advantages over silicones (polysiloxanes) in lubricity and bulk modulus. It is evident that incorporation of the silicon atom into the hydrocarbon skeleton can improve the utility of the structure for synthetic lubricant purposes.
However the desirable effects of the silicon atom in the monosilahydrocarbons of the prior art become attenuated as the alkyl chains therein are increased beyond a certain length. Monosilahydrocarbons containing for example ninety or more carbon atoms would almost certainly be solids, not fluids, at room temperature. Moreover obtaining the chemical raw materials (high molecular weight olefins or alkyl halides) in the necessary purity required for the syntheses of high molecular weight monosilahydrocarbons is extremely difficult. Thus, within the class of monosilahydrocarbon synthetic lubricant base stocks, it is the lower molecular weight members which are useful in applications wherein a lower fluid viscosity is required and where some degree of volatility can be tolerated. Liquid space lubricants, however, are frequently required to have extremely high viscosities and extremely low volatilities, and for such applications the monosilahydrocarbons of the prior art, because of their relatively low molecular weights, are not suitable.
It would be highly desirable to have available a class of silahydrocarbons which retain desirable characteristics of the monosilahydrocarbons of the prior art, but which could be prepared in a wider range of molecular weights, viscosities, and volatilities, so as to be suitable not only for the lower-viscosity applications currently satisfied by the prior art materials but for the high-viscosity low-volatility applications as well. It would be further desirable if this new class of silahydrocarbons could be prepared from readily accessible raw materials. It would be additionally desirable to have available relatively simple silicon-containing chemical intermediates, which by the proper choice of reagents could be converted into numerous silahydrocarbon structures designed to have properties suitable for specific applications. Our invention satisfies all of these objects.